Another unit originally designed for one of the Judith Edge industrials and one which can also be easily adapted for other loco types sharing the same 22mm wheelbase.
 
Unlike generic 'Spud' type motor bogies, the inter-linking mechansism is elevated, keeping the geartrain out of sight so you can preserve the space between the wheels - great for Sentinals, or other chain-driven prototypes.
 
It rides directly on the loco axles with the weight of the engine supported by the existing sideframes or chassis, allowing you to arrange one of the driven axles so it rocks, as part of a simple 3-point compensation system.
 
With a 2mm bore, push-fit axle gear of only 8.7mm diameter, 3 foot wheels can be used without problems.